linux-kernel - Re: [PATCH] PM / OPP: Call notifier without holding opp

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Message-ID: <20170920194720.GB457@codeaurora.org>
Date:   Wed, 20 Sep 2017 12:47:20 -0700
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>, cw00.choi@...sung.com,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        myungjoo.ham@...sung.com, inki.dae@...sung.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM / OPP: Call notifier without holding opp_table->lock

On 09/20, Viresh Kumar wrote:
> On 20-09-17, 10:00, Stephen Boyd wrote:
> > On 09/20, Viresh Kumar wrote:
> 
> > > diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
> > > index 4360b4efcd4c..668fd940d362 100644
> > > --- a/drivers/base/power/opp/core.c
> > > +++ b/drivers/base/power/opp/core.c
> > > @@ -1627,6 +1627,9 @@ static int _opp_set_availability(struct device *dev, unsigned long freq,
> > >  
> > >  	opp->available = availability_req;
> > >  
> > > +	dev_pm_opp_get(opp);
> > > +	mutex_unlock(&opp_table->lock);
> > 
> > Does this prevent the OPP from changing while the lock is
> > released?
> 
> No, its just ref counting and will only prevent it from getting freed.
> 
> There is only one thing that can change for an OPP though after it is
> created, its availability.

Ok.

> 
> > That would be the only difference from before. It's
> > possible that nobody cares about this situation though.
> 
> I am not sure if its worth caring for right now :)
> 
> Also the notifier chain will not start again until the previous call
> chain is finished. So we are kind of synchronized here.
> 

Yep. Just me worrying out loud. You can add my

Reviewed-by: Stephen Boyd <sboyd@...eaurora.org>

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